| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill for woodworking projecting a tip end drill 3 for positioning or the like at the center of the tip end of the drill main body 1 formed by a helical lead 2 and omitting a marking-off edge. SOLUTION: The tip end face of the drill main body 1 formed by the helical lead 2 is projected from the center side toward the periphery and is formed to be an inclined plane tilted in an angle corresponding to a relief angle toward the back of the direction of rotation from the side of the groove 6. Furthermore, a point of the drill 8 is formed nearer at the center side than the outer peripheral at the top face of the drill main body 1 by giving a chamfer 7 at the peripheral edge part of the top of the drill. A processed body cut deeply by the point of the drill 8 is bored by a first cutting edge 9 to the center direction from the point of the drill 8 and by a second cutting edge 10 to the outer periphery from the point of the drill 8. As the inner peripheral surface part of the bored hole is shaved by the second cutting edge with a narrow width, the inside surface can be bored to be a condition of clean surface. COPYRIGHT: (C)2004,JPO
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